This invention relates to a heat-shrinkable tube and a heat-shrinkable sheet each of which can be used for insulating and/or protecting a connecting portion between wires or cables, and to methods of shrinking the tube and sheet, respectively.
Generally, the cables have conductors and insulators coating on the conductors for insulating and protecting the conductors, respectively. In order to connect the cables to each other, the insulators must be partially removed from a connecting portion between the cables to establish electric connection between the conductors. Therefore, it is assumed that the conductors are exposed as an exposed part in the connecting portion.
For assuring electric insulation of the exposed part from surroundings, use is sometimes made of a heat-shrinkable tube. The heat-shrinkable tube is produced by a process comprising the steps of forming a thermoplastic polymeric material, such as polyethelene, into a tubular member having a tubular shape, cross-linking the thermoplastic polymeric material of the tubular member to an appropriate extent, expanding or stretching the tubular member at a temperature not lower than a softening point thereof to form an expanded tubular member having an expanded shape, and cooling the expanded tubular member to a room temperature with its expanded shape maintained. When the heat-shrinkable tube thus obtained is heated again to the temperature not lower than the softening point, the heat-shrinkable tube tries to recover its initial shape before expansion. In other words, the heat-shrinkable tube shrinks when it is heated. Therefore, if the heat-shrinkable tube is used in the connecting portion of interconnection between the cable and the object, it is possible to form a protection/insulation layer tightly fitted to an outer periphery of the connecting portion.
Through the similar process, a heat-shrinkable sheet is also produced and used in addition to the heat-shrinkable tube. The heat-shrinkable tube or the heat-shrinkable sheet is used not only in the connecting portion of interconnection between the cable and the object as mentioned above but also in various other fields.
In a heating operation for the purpose of shrinking the heat-shrinkable tube or the heat-shrinkable sheet when it is used, use may be made of a special electric heater designed therefor. Sometimes, an ordinary electric heater such as a hair drier or a gas torch is used. In the latter case, the result of the heating operation largely depends upon the skill of an operator. If uniform heating is unsuccessful, deformation or local xe2x80x9cscorchxe2x80x9d may be caused to occur. In the worst case, the tube will be broken.
In the meanwhile, a connecting operation for connecting a telephone cable extended between utility poles requires the operator to work at a high place. In this event, another risk is associated with such high-place work in addition to the above-mentioned trouble in the heating operation itself. Depending upon a working place, it may be very difficult to use the heater of the above-mentioned type in the heating operation.
It is therefore an object of this invention to provide a heat-shrinkable tube and a heat-shrinkable sheet which enable a shrinkage-inducing operation to be reliably and efficiently performed irrespective of the skill of an operator.
It is another object of this invention to provide a heat-shrinkable tube and a heat-shrinkable sheet which facilitate a heating operation.
It is still another object of this invention to provide a shrinking method for the heat-shrinkable tube and the heat-shrinkable sheet mentioned above.
Other objects of the present invention will become clear as the description proceeds.
According to an aspect of the present invention, there is provided a heat-shrinkable tube which comprises a tubular member being shrinkable in response to heat and having a cylindrical surface, and a thin film formed on at least a part of the cylindrical surface and made of a magnetic loss material which has a high magnetic loss characteristic. The thin film has a first phase comprising a first one of Fe, Co, and Ni and has a second phase comprising an insulator containing at least one element other than Fe, Co, and Ni.
According to another aspect of the present invention, there is provided a heat-shrinkable sheet which comprises a sheet member in response to heat and having a flat surface, and a thin film formed on at least a part of the flat surface and made of a magnetic loss material which has a high magnetic loss characteristic. The thin film has a first phase comprising a first one of Fe, Co, and Ni and has a second phase comprising an insulator containing at least one element other than Fe, Co, and Ni.
According to still another aspect of the present invention, there is provided a method of shrinking the heat-shrinkable tube, comprising the steps of disposing an oscillator in the vicinity of the thin film and making the oscillator irradiate electromagnetic radiation towards the thin film, so that the thin film generates the heat.
According to yet another aspect of the present invention, there is provided a method of shrinking a heat-shrinkable tube, comprising the steps of disposing a conductive wire in vicinity of the thin film and supplying an alternating current to the conductive wire to make the conductive wire irradiate electromagnetic radiation towards the thin film, so that the thin film generates the heat.
According to a further aspect of the present invention, there is provided a method of shrinking the heat-shrinkable sheet, comprising the steps of disposing an oscillator in the vicinity of the thin film and making the oscillator irradiate electromagnetic radiation towards the thin film, so that the thin film generates the heat.
According to a still further aspect of the present invention, there is provided a method of shrinking a heat-shrinkable sheet, comprising the steps of disposing a conductive wire in vicinity of the thin film and supplying an alternating current to the conductive wire to make the conductive wire irradiate electromagnetic radiation towards the thin film, so that the thin film generates the heat.